Stoker



Nov. 9, 1948. c.' E. SHAFFER 2,453,152

s-roxmn Filed Aug. 25, 1944 v 3 Sheets-Sheet 1 INVENT OR.

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Nov. 9,, 1948. c. E. SHAFFER 2,453,162

STOKER Filed Aug. 25, 1944 3 Sheets-Sheet 2 INVENTOR. SHflFFL-IE.

Nov. 9, 1948. c. E. SHAFFER 2,453,162

STOKER Filed Aug. 25, 1944 3 Sheets-Sheet 3 INVENTOR CHEs R 15. JHHFFSR.

Patented Nov. 9, 1948 UNITED STATES STOKER Chester E. Shaffer, Arlington, N. J., assignor, by

mesne assignments, to Koppel-s Company, Incorporated, Pittsburgh, Pa., a corporation of.

Delaware Application August 25, 1944, Serial No. 551,084

Claims.

The present invention relates, in general, to automatic heating apparatus employing solid fuels, and has reference more particularly to improvements in a stoker mechanism for automatically de-ashing the fuel bed.

The primary object of the present invention is to provide improvements for automatically deashing the fuel beds of domestic furnaces which are continuously fed with fuel in such manner that the fuel bed is kept substantially free of ash thereby preventing the formation of clinkers and making the fuel pieces readily available to combustion air.

Another object of the present invention is to provide a fuel stoker which will be operative for automatic removal of ash from a fuel bed.

It is a further object of the present invention to provide a simple, stationary inclined grate with means for maintaining the same at all times substantially free of ash accumulations so that the radiant heat of an incandescent fuel on the grate will be more completely and emciently employed.

Yet another object of the present invention is to provide a fuel-bed agitating device that is operative also to feed solid fuel to a fuel bed and that is eflective in agitating burning fuel, thus to shake ashes therefrom without having moving metal parts in contact with the burning fuel.

The invention has for further objects such operative advantages as may be found to obtain in the processes or apparatus hereinafter described or claimed.

In the accompanying drawings forming a part of this specification and showing for purposes of exemplification preferred apparatus and methods in which the invention may be embodied and practiced but without limiting the claimed invention specifically to such illustrative instance or instances:

Figure 1 is a diagrammatic elevational view with parts broken away, of an underfeed stoker which embodies an inverted truncated conical grate for around boiler and a'reciprocating fuelfeeding and ash-removal mechanism illustrating the preferred form of the invention.

Figure 2 is a diagrammatic plan view of the underfeed stoker mechanism shown in Figure 1;

Figure 2a is a fragmentary view showing for purpose of clarity the feed hopper and the swinging gate operating mechanism for closing the h pp r;

Figure 3 is a vertical section of the inverted, conical grate taken along line III-J11 of Figure 1;

Figure 3a is a fragmentary perspective view of the mouth of the underfeed stoker showing for purpose of clarity the shape of the ledge therein illustrated.

Figure 4 is a plan view and Figure 5 is a side elevational view of the improved grate bar employed in the conical grate illustrated in Figures 1, 2 and 3;

Figures 6 and 7 are cross-sectional views of the conical-grate bar taken along lines VI-VI and VII--VII of Figure 4;

Figure 8 is a diagrammatic elevational view in section of the automatic stoker and stationary conical grate, with parts broken away, illustrating the position of coke pieces in the apparatus whenthe feeder and fuel-bed agitator device is in a forward position, and when the grate is only partially full of coke;

Figure 9 is similar to Figure 8 and shows the position of coke-pieces in the said apparatus when the said feeder and fuel-bed agitator device is in a retracted position;

Figure 10 is a simplified diagrammatic elevational view of a modified form of the apparatus of the present invention which is particularly adapted to use with rectangular fire pots;

Figure 11 is a diagrammatic plan view, with parts broken away of the rectangular grate and taken along line XI-XI of Figure 10;

Figures 12 and 13 are respectively the plan and side views of one of the side grate bars of the rectangular grate;

Figures 14 and 15 are respectively the plan and side views of one of the end grate bars of the rectangular grate; and

Figures 16 and 17 are respectively the plan and side views of one of the corner grate bars of the said rectangular grate.

The same characters of reference designate the same parts in each of the views of the drawings.

Referring more particularly to Figures 1, 2 and 2a, an automatic stoker I0 is shown in combination with a stationary inverted truncated conical grate ii that is located in the circular fire pot I! of a boiler. Solid fuel is fed by the said stoker Ill from'a bin H to the fuel entrance at the base of the grate H by means of two reciprocating plates i6 and I1, that are disposed in, respectively, stoker tube It and a trough-shaped covered conduit Ill. The plate ll serves to deliver the fuel from the fuel bin H to the tube II and the plate It delivers the fuel from plate H to the grate II. The reciprocating plates are both 66 driven by a motor 20 through means comprising a gear reducer 2!, a crank 22, and a connecting rod 23 connecting the crank 22 to a driving arm 21%. The said arm 24 is bolted to a heel plate 26 that is at the outer end of, and forms a part of, the. reciprocating plate Hi. The plates l6 and 26 move together to carry fuel delivered thereto from the plate H, to the grate ll. The arm 24 on the heel plate 26 is also connected by a connecting link with a circular drive ring 21. The drive ring 27 is connected by a rod 28 (Figs. 1 and 2a) to the outer end of plate I1. With this construction the reciprocation of the driving arm 26 will simultaneously reciprocate plates IB and I7.

The said drive ring 21 is perforated with numerous bolt holes 29 to one of which, depending upon the angular relationship of conduit ill to tube E8, the inner end of the rod 28 may be connected. By this arrangement the stoker may be located between a fuel bin and ash-pit doors having different angular arrangements.

The feed plate l'l conveys fuel from bin M to a hopper 30 which is formed by the rounded end of the conduit l9 and is set into the outer end of the stoker tube I8. The coke-pieces delivered to the hopper 30 will fall upon the conveyor feed plate 16.

The hopper 30 is provided with a swinging gate 3| that is opened on the forward stroke of the conveyor plate ii to permit coke to pass from the conveyor plate into the hopper. To accomplish this a lug 32 that is secured to the rod 28 engages an arm 33 fixed on the pivot rod 3M of the gate 3| and opens positively the gate when the conveyor plate moves forward. A counterweight 35 is secured to the said pivot rod em and moves the gate into closed position when the conveyor plate is moved rearwardly on its return stroke. As the gate 3i is opened, coke delivered by the conveyor plate 11 falls down the inclined side of hopper 30.to the heel plate 26 and conveyor plate It. It is desirable to maintain the gate 3| closed as much as possible in order to prevent infiltration of air through the conveyor tube to the furnace. The inclined side of the hopper 30 is disposed at an angle greater than the angle of repose of coke so that no coke pieces will remain on the plate 3% to prevent the closing of the gate 3|.

The coke falls through the hopper 30 and is pushed forward in the tube i8 as the plates 26 and i6 are moved in the forward stroke. On the rearward stroke of the reciprocating plate It the coke is held from rearward movement by a wall 35 which forms the back end of the stoker tube. l8. On the front end of the feed plate I6 is mounted a pusher head 36 which has a rearwardlysloping face 38. The pusher head 36 rides on the bottom of an elbow section 39 of the stoker tube and has a substantial thickness with a recess in its upper face so that the conveyor plate is attached therein with the upper surface of the conveyor plate in the same plane as the top surface of the pusher head. The reciprocating pusher head acts positively to push the coke through the elbow of the stoker up into the fuel bed.

vThe construction and arrangement of the elbow section 39 form an important feature of the present invention. The front edge of the top of the stoker tube i8 projects into the throat of the elbow and forms a semi-circular projecting edge 40, as shown more particularly in the per spective view, Fig. 3a. The said projectingedge 40 of the stoker tube I8 is arcuate, or as aforesaid semi-circular, in vertical section conforming thereby to the rounded top of the tube It and it projects into the said throat of the stoker elbow to form a ledge which cuts ofl (as seen in plan view in Figures 2 and 11) the entrance into the i'uel bed, so that the so-formed ledge will act as an impost temporarily to support coke arches I which form at the entrance of the fuel bed. When the coke is moved forwardly by the pusher head as and the plate It it moves up the circular face of the elbow and enters the fuel bed. As the coke moves upwardly in the fire pot. the projecting edge 60 tends to form arches which hold the coke against a rearward or falling movement during the forward stroke of the pusher head 36.' The position of the coke at the end of the forward stroke is illustrated in Figure 8. On the rearward stroke of the pusher the support which is provided by the pusher head 36 is removed. When this support is withdrawn, coke which is held up by the projecting edge 60 suddenly falls and allows coke in the fuel bed to drop down into the elbow section 39 into the position illustrated in Figure 9. This movement is important because it imparts to the coke within the fuel bed a reciprocating up and down movement across the face of the openings of the grate. Any ash that is contained in the fuel tively to heat the water in the boiler.

bed is worked out to the grate and the movement of the fuel insures that the ash will fall through the grate. -Thus the movement of the fuel bed keeps the grate clean and the ash out of the bed.

This action (continuous ash removal by the newly provided fuel bed movement) not only keeps the fuel bed free of ash but it provides a heat radiating surface around the fuel bed unimpaired by ash accumulation from which surface heat is radiated to the boiler walls efiec- The contact of hot fuel without an intervening layer of insulating ash also tends to keep the grate bars at high temperature but here their inclined disposition in close spatial relation to the watercooled boiler walls provides for the effective cooling of the grate bars by radiation of heat therefrom to the said boiler walls.

Although the movement of the pusher is slow and only brings into the stoker tube I8 from three to five pieces of coke per stroke, the rearward motion of the pusher head permits a breaking of the described arch which produces an abrupt fall of the coke in the fuel bed and thus provides the described fuel bed agitation.

' The ash falls through the conical grate into an ashplt which is beneath and surrounds the stoker. This ash is conveyed from the pit into an ash-storage bin 42 which'is located beneath the stoker tube [8. The movement of the ash is carried out by means of reciprocating slats 43 that are slidably mounted in guides 44 which are positioned under the stoker elbow 39. The slats are secured to a bracket 45 which is attached to the underside of the feed plate It.

Therefore thereciprocating movement of the feed plate also domestic size.

to the upper end of the elbow section 39. The

upper ends of the grate bars rest against the wall of the inner surface of the furnace. Each bar 41 is provided with six slots 48 through which the ash is removed from the fuel'bed and through which air is introduced thereinto. The slots 48 are designed to provide a high ratio of open grate area to dead area and are perforated obliquely to the plane of the surface of the grate bar so that the end Walls of the slots are substantially vertical when the bars are in position in the grate, thus to prevent hold-up ofash on the said end walls, Each grate bar is providedwith a tapered lug 49 which fits into a corresponding opening 50 on the side of the adjacent grate bar so that the bars are locked together when they are as sembled.

A modified form of apparatus forming a part of this invention is illustrated in Figures to 17 inclusive. This modified form is adapted more particularly as a stoker apparatus for a rectang'ular boiler. The stoker and firebox difler principally in the shape of the grate and the stoker elbow which are altered to conform to the requirements of a rectangular firebox. To accomplish this three different types of grate bars are required to form the grate. Figures 12 and 13 illustrate a rectangular shaped grate-bar that is employed in positions on each side of the elongatedoval-formed bottom of the grate. The positions of these grate bars are illustrated at 55, 56, 51, and 58 in Figure 11. These bars have a notched base portion 59 to rest in. asupporting ring 60 that is secured to the top of the stoker elbow 6|. Figures 16 and 17 illustrate a diamond shaped grate bar which is used at the corners of the rectangular firebox, such as illustrated at the points 62, 63, 64, and 65, of Figure 11. These diamondshaped bars have a notched base 66 which rests in the supporting ring 60. At each side of the corner bars are located trapezoidal-shaped grate bars which are shown in detail in Figures 14 and 15. Two bars are required for each corner such as illustrated at 61, 68, 69, 10, ll, 12, I3 and 14 in Figure 11. The trapezoidal-shaped bars have a notched base 15 which fits into the supporting ring 60. It will be understood that all of these grate bars are provided with slots or openings to permit the movement of ash through the grate and to permit the admission of air for supporting combustion. The upper faces of these grate bars rest against the wall of the boiler, such as illustrated in Figure 10. The corner grate and the adjacent trapezoidal-shaped bars illustrated in respectively Figure 16 and Figure 14 are sodesigned that the angle of elevation of the grate is not materially reduced at the corners of the rectangular firebox even though a considerably longer slant height, from supporting ring to furnace wall, is there encountered.

The angle of elevation of the grate bars of the present invention, for both the rectangular and truncated-conical grates, whereby there is pro-,- vided optimum conditions of combustion and radiation therefrom along with minimum accumulation of ash or production of clinker, has been found to be at least more than approximately 50 when the fuel employed is coke of customary Variations in size of heaters and grates therefor, and in the relative size of devices of the stoker apparatus and more particularly of the said plunger head in relation of the area of the fire-bed fuel entrance will prescribe deviations in the above defined angle of elevation, which said deviation can be readily determined by sim- I less conducive to their formation It is believed from observation of stoker operation, that the angle of elevation of the grate bars must be sufiiciently steep that lines of force from the moving plunger head will be directed to, and will move, the fuel pieces lying on the grate; and that this requirement will be satisfied when the angle of elevation is, within reasonable limits, the complement of the angle of repose 0f the employed fuel. Variation in the form, size, and relative duration of the described arch and in the resultant eflicacy in ash removal of the falling of the arch of course occurs, and thus the above description is not intended to be limiting but is offered merely to augment the explanation of the action of the apparatus in providing automatic ash removal as well as automatic fuel feeding.

I As used in the following claims, the term furnace is intended to include house-heaters of all types employing solid fuel.

The invention as hereinbefore set forth is embodied in particular'form and manner but may be variously embodied within the scope of the claims hereinafter made.

I claim:

1. In a fuel combustion chamber, the combination of: a stationary grate having an upwardly increasing cross-sectional area determined 1 said central fuel opening; and means, including the said ledge and a reciprocating plunger device, operative automatically both to raise and sharply to drop a fuel bed in said grate, thereby causing combustion residues to travel downwardly through fuel interspaces of said fuel bed and also through the spaces between said bar-like members.

2. In a fuel combustion chamber, the combination of: a stationary grate having an upwardly increasing cross-sectional area determined by spaced bar-like members that are disposed about a central fuel-opening at the base of the said grate; a reciprocatory plunger which, by intermittently coming into contact with, and shortly thereafter leaving the contact of fuel lying at the entrance to the said fuel-opening and beneath fuel in a fuel bed in said grate, is operative to agitate the said fuel bed; and a protruding ledge extending across an arc of the ring about the said central fuel-openin at the fuel-inlet end thereof, and acting as an impost for momentary support of arches of fuel formed in the said opening.

3. Apparatus for automatic heating with solid fuel, said apparatus comprising the combination of: an underfeed stoker having a reciprocatory plunger that is operative both to push fuel into the fuel bed and to raise and release in successive operation a fuel bed of the so-fed fuel; an inclined, stationary grate havingan upwardly increasing horizontal cross-sectional area determined by bar-like members that are disposed about a central fuel opening at the base of the said grate and that are inclined at an angle of elevation equal to at least about fifty degrees;

7 and a projecting ledge that extends horizontally from an arc-portion of the ring about the said central fuel opening, cuts 011, a minor portion of the area of the said opening and acts in cooperation with the said plunger when the same is in forward position as an impost momentarily to support arch'es of the said fuel formed in the said opening, but is inefiectual to support such arches when the said plunger is in retracted position, whereby the said arches fall and the fuel bed is sharply agitated.

s. Apparatus as claimed in claim 8 wherein the shape of the said stationary grate conforms to an inverted truncated cone.

5. In a fuel combustion chamber, the combination of: a grate having an upwardly increasin cross-sectional area determined by spaced bar-like members arranged about a central fuel openin at the base of the said grate; a protrudsaid ledge and to raise and sharply to drop a fuel bed in said grate, thereby causing combus- REFERENCES CITED The following references are of record in the Number Name Date 687,656 Schneider Nov. 26, 1901 1,149,611 Amsler Aug. 19, 1915 1,722,495 Chapman July 30, 1929 1,887,191 Whitney Nov. 8, 1932 1,946,850 Goss et 91 Feb. 13, 1934 2,067,583 Stark Jan. 12, 1937 2,106,621 Paige Jan. 25, 1988 2,163,291 Raddatz June 20, 1939 2,166,080 Snyder et ai July 11, 1939 2,361,888

Snyder Oct. 81, 1944 

